1. Field of the Invention
The present invention relates to a double wire cord composed of a first cord and a second cord that can be separated from each other, and a portable audio device using the double wire cord, such as earphones and headphones.
2. Description of the Related Art
A conventional double wire cord that is composed of a pair of wire cords that can be separated from each other and used for stereo earphones, headphones or the like is described in Patent Documents 1-4.
In the Patent Document 1, a technique concerning stereo headphones using a double wire cord with a fastener is described. Each of the two headphone ear pieces for stereo is connected to one end of a corresponding one of the two wire cords, and the other ends of the wire cords are connected to a plug together.
The fastener is composed of a slider and two bands of tape that can be separated from each other by moving the slider. The two bands of tape of the faster are each formed into a sleeve, and each wire cord is passed through its corresponding sleeve, thereby forming the double wire cord with the fastener. Each of the two headphone earpieces is electrically connected to one end of a corresponding one of the two wire cords of the double wire cord with the fastener, and the other ends of the wire cords are fixed together with a clamp and electrically connected to a plug, thereby forming a set of headphones.
Since the wire cords of the headphones can be separated from each other by moving the slider, the length of the branched wire cords can be easily adjusted, and the wire cords can be conveniently housed without getting tangled.
As technology relevant to the patent document 1, the stereophonic earphone cable indicated by the patent documents 2-4 is also known. The stereophonic earphone cable is the technology about the cable in which combination or separation is possible.
However, in the double wire cord indicated by the conventional patent documents 1-4, since form and structure are complicated, mass production is difficult and becomes a cost overrun. In order to combine the double wire cord, it is necessary to unite the position of the joint part of two wire cords, and the slider for combination is needed if needed. Thereby, the number of parts increases , and mass production is difficult and becomes a cost overrun. In addition, when the double wire cord is combined, the form of the section of the combined whole double wire cord becomes large, and bending comes to be hard again. As a result, when bending was repeated by force to the combined double wire cord, there was a possibility that the two combined wire cords might dissociate mutually, and problems that it was hard to use occurred.
[Patent Document 1] Japanese Patent Laid-Open No. 2004-56636
[Patent Document 2] Japanese Patent Laid-Open No. 7-211146
[Patent Document 3] U.S. Pat/ No. 6,751,382
[Patent Document 4] European Patent Laid-Open No. 1,509,062